Nearly all government-funded insulation installs have failed — 98% need repairs! Learn how poor regulation led to this crisis and how Viridian does things differently.
Home insulation failures: 98% of government installs need repairs
Estimated reading time: 2 minutes
A wake-up call for homeowners
A recent audit by the National Audit Office (NAO) has revealed a shocking reality – nearly all homes that received external wall insulation under government schemes between 2022 and the beginning of 2025 now need repair or replacement (98% of them!). Even cavity wall insulation installations have a failure rate of almost 30%.
These are not isolated cases, instead they point to failings in quality control by relevant regulatory bodies, government oversight, and contractor selection. Homeowners are left to deal with damp, mould, health and structural risks.
At Viridian, we believe insulation should solve problems, not cause them. Here’s what homeowners need to know to protect themselves. First, we need to clarify the differences between cavity wall and external wall insulation, what properties they are suitable for, and the costs involved.
Cavity vs external wall insulation – what is the difference?
Cavity wall insulation (CWI)
- Installation: Insulation material is injected within the cavity between the inner and outer walls; the process is less intrusive than external wall insulation
- Suitability: Properties built with existing wall cavities (those are typically post-1920s homes)
- Complexity and price: Less intrusive, quicker to install, and often more cost-effective
- Safer in many cases: Given recent failures, CWI offers lower risk if the home structure is suitable at a lower price point with minimal disruption to your property
External wall insulation (EWI)
- Installation: The insulation material is fixed to the outside of the building and finished with render or cladding
- Suitability: Properties with solid walls without a cavity
- Complexity and price: Requires scaffolding, careful sealing, and professional finishing; usually more expensive than CWI
- Causes of failure: The recent audit suggests nearly 98% of EWI cases need repair. Poor detailing, weak waterproofing, or shoddy substrate prep were the most commonly identified reasons
What went wrong & why it matters
The NAO report highlights weak regulatory control, unclear certification systems, and fraudulent practices as main reasons for the installation failures. Because of these uncertainties and lack of regulation, many installations were rushed and carried out poorly.
The consequences of these actions are dire – homes are suffering from moisture, poor thermal performance, health concerns, and safety risks like blocked ventilation or exposed wiring.
This exposes a harsh truth – home insulation is only as good as its quality, the materials used, and the installer’s integrity.
Viridian’s commitment is to you and your home
At Viridian, we specialise in cavity wall insulation and take pride in delivering solutions that are thoroughly assessed and expertly installed to help you achieve a warmer, more comfortable, and energy-efficient home.
Every job is completed by our own NVQ-qualified installers, ensuring full accountability from survey to completion.
Here are a few things to look out for when looking for the right home insulation company for your home:
- It all starts with the survey: At Viridian, we take pride in our industry-leading survey process – it is quick, seamless and fully digital (and completely free!). This means that you receive your detailed post-survey quote instantly with all the information you need to make your decision
- Choose certified installers: Viridian is a PAS 2030:19 and TrustMark-accredited company. This means we adhere to existing industry standards in order to provide an excellent finish to any job. We also have stringent internal policies and quality control procedures that ensure our customers receive long-term value out of our services
- Request documentation and guarantees: We offer a 25-year cavity wall insulation guarantee which is backed by an independent guarantee provider. Not only that, but we also offer our own company-backed guarantees that ensure the materials used and workmanship are all up to excellent industry standards. If anything does go wrong, our team will come back and rectify any issues completely free of charge within the specified time frame of the guarantee
Book your free cavity wall survey now